Heretofore, it has been not unusual for a portable conveyor system to run between a continuous mining machine and a fixed terminus of a main conveyor system which transports coal to the earth's surface. In some instances, there are extensible floor-supported belt systems, such as disclosed in the patent to Moon U.S. Pat. No. 2,986,266, and in other instances they are roof-supported monorail systems, such as shown in Craggs U.S. Pat. No. 3,920,115. In room-and-pillar coal mining, a major problem results from the prohibition against working beneath an un-bolted or unsupported roof.
Assuming that a continuous mining machine makes two side-by-side ten foot wide cuts, and assuming further that a portable extensible conveyor is connected either directly behind the miner or to a surge car; usually the continuous miner, after cutting in about eighteen feet, must back out of the cut and move to another location while the roof bolter operates, and then moved back to resume the cut. This entails re-arrangements of the conveyor and discontinuous face-haulage.